Ferrite sintered plate and ferrite sintered sheet

Abstract

The present invention relates to a ferrite sintered plate having a composition comprising 47 to 50 mol % of Fe 2 O 3 , 7 to 26 mol % of NiO, 13 to 36 mol % of ZnO, 7 to 12 mol % of CuO and 0 to 1.5 mol % of CoO, as calculated in terms of the respective oxides, in which the ferrite sintered plate has a volume resistivity of 1×10 8 to 1×10 12 ·cm and a thickness of 10 to 60 μm; and a ferrite sintered sheet comprising the ferrite sintered plate on a surface of which a groove or grooves are formed, and an adhesive layer and/or a protective layer formed on the ferrite sintered plate, in which the ferrite sintered sheet has a magnetic permeability at 500 kHz a real part of which is 120 to 800 and an imaginary part of which is 0 to 30, and a product (μm) of the real part of the magnetic permeability at 500 kHz of the ferrite sintered sheet and a thickness of the ferrite sintered plate is 5000 to 48000. The ferrite sintered plate and the ferrite sintered sheet according to the present invention have a high volume resistivity as well as a large μ′ value and a small μ″ value of a magnetic permeability thereof, and therefore can be suitably used as a shielding plate in a digitizer system.

The invention claimed is: 
     
       1. A ferrite sintered plate which has a composition comprising 47 to 50 mol % of Fe 2 O 3 , 7.0 to 15.1 mol % of NiO, 13 to 36 mol % of ZnO, 7.0 to 12 mol % of CuO and 0 to 1.5 mol % of CoO, as calculated in terms of the respective oxides, which has a volume resistivity of 1×10 8  to 1×10 12  Ω cm and which has a thickness of 10 to 60 μm, wherein the ferrite sintered plate has a magnetic permeability at 500 kHz a real part of which is 296 to 1200 and an imaginary part of which is 0 to 90. 
     
     
       2. The ferrite sintered plate according to  claim 1 , wherein a product (μm) of the real part of the magnetic permeability at 500 kHz of the ferrite sintered plate and a thickness of the ferrite sintered plate is 7500 to 72000. 
     
     
       3. The ferrite sintered plate according to  claim 1 , wherein at least one groove is formed on at least one surface of the ferrite sintered plate and the depth of the at least one groove is 1/20 to ¼ of a thickness of the ferrite sintered plate. 
     
     
       4. A ferrite sintered sheet comprising the ferrite sintered plate according to  claim 1 , and an adhesive layer or a protective layer which is formed on at least one surface of the ferrite sintered plate. 
     
     
       5. A ferrite sintered sheet comprising the ferrite sintered plate according to  claim 1 , an adhesive layer formed on one surface of the ferrite sintered plate, and a protective layer formed on the other surface of the ferrite sintered plate. 
     
     
       6. A ferrite sintered sheet comprising the ferrite sintered plate according to  claim 1 , and adhesive layers respectively formed on opposite surfaces of the ferrite sintered plate. 
     
     
       7. A ferrite sintered sheet comprising the ferrite sintered plate according to  claim 1 , and protective layers respectively formed on opposite surfaces of the ferrite sintered plate. 
     
     
       8. The ferrite sintered sheet according to  claim 4 , wherein the ferrite sintered plate is partitioned into small pieces. 
     
     
       9. The ferrite sintered sheet according to  claim 8 , wherein the ferrite sintered sheet has a magnetic permeability at 500 kHz a real part of which is 120 to 800 and an imaginary part of which is 0 to 30, and a product of the real part of the magnetic permeability at 500 kHz of the ferrite sintered sheet and a thickness of the ferrite sintered plate is 5000 to 48000. 
     
     
       10. A digitizer system comprising a detector and a shielding plate disposed adjacent to the detector, in which the shielding plate is constituted of the ferrite sintered plate according to  claim 1 . 
     
     
       11. A digitizer system comprising a detector and a shielding plate disposed adjacent to the detector, in which the shielding plate is constituted of the ferrite sintered sheet according to  claim 4 .